Process for the removal of metal or impurities from electric arc furnace dust

ABSTRACT

A method for preparing Electric Arc Furnace dust (EAFD) for metal recovery, comprising: a) mixing the EAFD comprising zinc oxide or lead oxide, or a mixture of both, with a liquid and a binder to produce an EAFD mixture; b) producing a shaped EAFD pellet; and c) drying the shaped EAFD pellet is disclosed. A method for recovering zinc from Electric Arc Furnace dust (EAFD), comprising: a) heating the EAFD comprising at least one metal comprising zinc in an inert gas atmosphere at a temperature ranging from 700° C. to 1100° C.; and b) evaporating the at least one metal comprising zinc from the EAFD and collecting the at least one metal is also disclosed. A method for recovering an impurity from Electric Arc Furnace dust (EAFD), comprising: a) heating the EAFD comprising an impurity in an inert gas atmosphere at a temperature ranging from 700° C. to 1100° C.; and b) evaporating the impurity from the EAFD and collecting the impurity is also disclosed. A method for recovering iron oxide from Electric Arc Furnace dust (EAFD), comprising: a) heating the EAFD comprising iron oxide and at least one metal in an inert gas atmosphere at a temperature ranging from 700° C. to 1100° C.; and b) separating the iron oxide by evaporating the at least one metal from the EAFD and leaving the iron oxide as a residue is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/816,987, filed on Apr. 29, 2013, which is incorporated herein by reference in its entirety.

BACKGROUND

Electric Arc Furnace Dust (EAFD), in one aspect bag house dust (BHD), constitutes one of the largest industrial waste materials produced. Several approaches are used for the treatment of the EAFD. Numerous alternatives of pyrometallurgical and hydrometallurgical approaches have been examined for treatment of the EAFD in the last few decades. Some commonly used and commercially successful pyrometallurgical process include the Waelz Kiln and similar advanced processes that involve the reduction of EAFD with coke or coal, lime and silica in rotary kiln furnaces. However, these processes are very energy intensive, resulting in high treatment cost, which can make them unfavorable for stand-alone, on-site treatment of dust at most steel mills. Hydrometallurgical processing that involves acidic and/or caustic leaching followed by precipitation of metals can be less expensive and energy consumptive, but generates considerable environmentally objectionable effluent and the yield is much lower than that of the pyrometallurgical routes. Some hybrid-combining pyre-metallurgy and hydro-metallurgy approaches and specific technologies, like Integrated Ezinex®, Enviroscience MetWool, Ausmelt, Enviroplas, etc. were developed and trialed recently. However, the capital and processing costs of these methods can be high.

Today, steel plants world-wide are concerned about the handling, storage and safe disposal of their waste materials including bag house dust (BHD), which is listed as a hazardous material (KO61) by International environmental protection agencies (IEPA). The problem encountered in the processing of BHD is one of finding an economical method of separating the zinc from the remainder of the dust, which consists mainly of iron, manganese, nickel, silicon and smaller quantities of other elements. Typically, BHD is a liability for steel makers. All the existing Zn extraction processes including pyrometallurgical, hydrometallurgical or hybrid processes are very expensive and the cost to process BHD ranges from $50-$250 per ton. The cost of production of Zn is also very high. Zn in BHD is present either in the form of zinc oxide (ZnO) or zinc ferrite (ZnO.Fe₂O₃). Removing zinc from a bimetallic compound, such as zinc ferrite (ZnO.Fe₂O₃), is more difficult than removing zinc from a mixture of zinc oxide and iron oxide, when zinc and iron are present as discrete compounds.

The removal and recovery of Zn, Pb, and/or Cd, etc. (so called “tramp” elements), from the impurities of, Cl, Na, and/or K, introduced in steel making processes and collected as BHD, while environmentally desirable, cannot be currently achieved by low cost technologies. Thus, a scalable and cost-effective dust treatment process and metal extraction from Electric Arc Furnace Dust is desired.

SUMMARY

In accordance with the purpose(s) of the invention, as embodied and broadly described herein, the invention, in one aspect, relates to a method for recovering a metal oxide from Electric Arc Furnace dust (EAFD), comprising:

-   -   a) mixing the EAFD comprising zinc oxide or lead oxide with a         liquid and a binder to produce an EAFD mixture;     -   b) producing a shaped EAFD pellet; and     -   c) drying the shaped EAFD pellet.

The invention disclosed here in another aspect relates to a method for recovering zinc from Electric Arc Furnace dust (EAFD), comprising:

-   -   a) heating the EAFD comprising at least one metal comprising         zinc in an inert gas atmosphere at a temperature ranging from         700° C. to 1100° C.; and     -   b) evaporating the least one metal comprising zinc from the EAFD         and collecting the at least one metal.

The invention disclosed here in a further aspect relates to a method for recovering an impurity from Electric Arc Furnace dust (EAFD), comprising:

-   -   a) heating the EAFD comprising an impurity in an inert gas         atmosphere at a temperature ranging from 700° C. to 1100° C.;         and     -   b) evaporating the impurity from the EAFD and collecting the         impurity.

The invention disclosed here in yet another aspect relates to a method for recovering iron oxide from Electric Arc Furnace dust (EAFD), comprising:

-   -   a) heating the EAFD comprising iron oxide and at least one metal         in an inert gas atmosphere at a temperature ranging from 700° C.         to 1100° C.;     -   b) separating the iron oxide by evaporating the at least one         metal from the EAFD and leaving the iron oxide as a residue.

While aspects of the present invention can be described and claimed in a particular statutory class, such as the system statutory class, this is for convenience only and one of skill in the art will understand that each aspect of the present invention can be described and claimed in any statutory class. Unless otherwise expressly stated, it is in no way intended that any method or aspect set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not specifically state in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including matters of logic with respect to arrangement of steps or operational flow, plain meaning derived from grammatical organization or punctuation, or the number or type of aspects described in the specification.

Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or can be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying figures, which are incorporated in and constitute a part of this specification, illustrate several aspects and together with the description serve to explain the principles of the invention.

FIG. 1 shows a flow diagram for the Caustic Soda Leaching Process for the extraction of zinc from EAFD of one aspect of the invention herein.

FIG. 2 shows the relationship between the weight loss from a BHD pellet and the temperature at which the pellet is sintered in a N₂ atmosphere for one aspect of the invention herein.

FIG. 3 shows the relationship between the weight % content of Zn remaining in a BHD pellet after sintering at various temperatures in a N₂ atmosphere for one aspect of the invention herein.

FIG. 4 shows the relationship between the Zn and Pb content of pellets sintered at various temperatures under nitrogen for one aspect of the invention herein.

FIG. 5 shows the Zn and Pb content of vapors extracted from BHD pellets sintered under N₂ at various temperatures for one aspect of the invention herein.

FIG. 6 shows the relationship between the weight of Zn removed from a BHD pellet sintered in a N₂ atmosphere at various temperatures for one aspect of the invention herein.

FIG. 7 shows the weight loss of Pb, Na, K, and Cl from a BHD pellet sintered at various temperatures under N₂ for one aspect of the invention herein.

DESCRIPTION

The present invention can be understood more readily by reference to the following detailed description of the invention and the Examples included therein.

Before the present compounds, compositions, articles, systems, devices, and/or methods are disclosed and described, it is to be understood that they are not limited to specific synthetic methods unless otherwise specified, or to particular reagents unless otherwise specified, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, example methods and materials are now described.

All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided herein can be different from the actual publication dates, which can require independent confirmation.

A. DEFINITIONS

As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a functional group,” “an alkyl,” or “a residue” includes mixtures of two or more such functional groups, alkyls, or residues, and the like.

Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, a further aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms a further aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. For example, if the value “10” is disclosed, then “about 10” is also disclosed. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

References in the specification and concluding claims to parts by weight of a particular element or component in a composition denotes the weight relationship between the element or component and any other elements or components in the composition or article for which a part by weight is expressed. Thus, in a compound containing 2 parts by weight of component X and 5 parts by weight component Y, X and Y are present at a weight ratio of 2:5, and are present in such ratio regardless of whether additional components are contained in the compound.

A weight percent (wt. %) of a component, unless specifically stated to the contrary, is based on the total weight of the formulation or composition in which the component is included.

As used herein, the terms “optional” or “optionally” means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; and the number or type of embodiments described in the specification.

It is understood that the compositions disclosed herein have certain functions. Disclosed herein are certain structural requirements for performing the disclosed functions and it is understood that there are a variety of structures that can perform the same function that are related to the disclosed structures, and that these structures will typically achieve the same result.

As used herein, the term “green strength testing” typically refers to a test that measures the ability of green pellets to remain intact during handling. In one test in this disclosure, a pellet is dropped a number of times from the height of 30 cm on a flat steel plate until it breaks. As used herein, the term “drop number” typically refers to the number of times before it breaks.

As used herein, the term “green pellets” typically refers to the pellets comprising moisture. The term can refer to pellets produced by balling action in a rotating disk or drum comprising moisture before drying or heating.

As used herein, the terms “sintered” or “sintering” typically refers to heating to a specific temperature and holding for a specific time in a furnace in certain gaseous or air atmosphere.

As used herein, the term “binder” typically refers to a compound or composition that aids in binding the powder and formulation of pellets, which can be spherical, in the presence of a specific amount of water. Such binding preparation can be, for example, during balling in a rotating disk or drum.

As used herein, the term “inert gas atmosphere” typically refers to an atmosphere of non-reactive gases such as nitrogen, argon, xenon, or krypton, and the like.

As used herein, the term or phrase “electric arc furnace dust” or “EAFD” is a term of art and refers to a solid by-product or material produced from a furnace steelmaking process, and is intended to encompass by-products and materials generated from all steelmaking operation phases and sources, such as, for example, scrap iron furnaces or sponge iron furnaces.

As used herein, the term or phrase “bag house dust” or “BHD” is a term of art and refers to a type of electric arc furnace dust generated in Saudi Arabia, which may, in various aspects, have similar or differing chemical compositions than electric arc furnace dusts produced from different countries. The bag house dust can be collected in a bag house, also called a bag house filter.

ABBREVIATIONS AND ACRONYMS BHD Bag House Dust

° C. degrees Celsius

C&S Analyzers Carbon & Sulphur Analyzer

DRI Direct reduced iron

EAF Electric Arc Furnace EAFD Electric Arc Furnace Dust

g gram(s) IEPA International environmental protection agencies kgf Kilogram force XRD techniques X-Ray Diffraction

XRF X-Ray Fluorescence

1. Electric Arc Furnace Dust (EAFD)

In various aspects, the disclosed compositions comprise by-products produced from a steelmaking process. In one aspect, the disclosed compositions comprise by-products produced from an electric steelmaking process. In a further aspect, the by-products comprise electric arc furnace dust (EAFD). In a still further aspect, the electric arc furnace dust (EAFD) comprises EAFD produced in various regions, for example, EAFD from North America or Europe or the Middle East. In a yet further aspect, the EAFD comprises EAFD of varying compositions depending on the type of scrap used, type of additives used during the production stage and the type of steel manufacture. For example, in one aspect, the EAFD comprises EAFD generated in Saudi Arabia, also referred to as bag house dust (BHD). In a further aspect, the EAFD comprises unstabilized, untreated EAFD. In a still further aspect, the EAFD comprises stabilized, untreated EAFD. In a yet further aspect, the EAFD comprises treated EAFD. In an even further aspect, the disclosed compositions comprise at least one additional by-product, for example, fly ash, blast furnace slag, or silica fume, or the like. An exemplary, non-limiting EAFD comprises one or more components comprising Fe, Zn, Pd, Cr, Cd, Mn, Cu, Si, Ca, Mg, Al, C, Na, or K or a mixture thereof. When the component is present, the EAFD comprises Fe in an amount ranging from 10 wt % to 60 wt %, Zn in an amount ranging from 2 wt % to 50 wt %, Pd in an amount ranging from 0.40 wt % to 15.14 wt %, Cr in an amount ranging from 0.2 wt % to 11 wt %, Cd in an amount ranging from 0.01 wt % to 0.3 wt %, Mn in an amount ranging from 1 wt % to 5 wt %, Cu in an amount ranging from 0.01 wt % to 0.3 wt %, Si in an amount ranging from 1 wt % to 5 wt %, Ca in an amount ranging from 1 wt % to 25 wt %, Mg in an amount ranging from 1 wt % to 12 wt %, Al in an amount ranging from 0.1 wt % to 4 wt %, C in an amount ranging from 0.11 wt % to 2.36 wt %, Na in an amount ranging from 0.5 wt % to 5 wt %, and K in an amount ranging from 0.35 wt % to 7 wt %.

In one aspect, a typical chemical composition of the EAFD is as follows:

Elements Wt % Fe₃O₄ 47.44 ZnO 19.36 Na₂O 2.52 MgO 5.85 CaO 6.63 K₂O 4.64 SiO₂ 4.75 Cl 1.70 PbO 1.89 MnO 1.79 SO₃ 1.16 Al₂O₃ 1.34 Cu 0.26 C 0.72

In one aspect, an exemplary, non-limiting composition of EAFD can include 29 wt % of Zn, 0.3 wt % of Cu, 4 wt % of Pb, 0.07 wt % of Cd, 25 wt % of Fe, 4 wt % of Cl, 3 wt % of MnO, and 3 wt % of SiO₂.

In one aspect, an exemplary, non-limiting EAFD, as measured using optical emission via Inductive Coupled Plasma (ICP), X-ray diffractometry (XRD), and Mossbauer spectroscopy analysis exhibits the following composition: ZnFe₂O₄, Fe₃O₄, MgFe₂O₄, FeCr₂O₄, CaO.15Fe_(2.85)O₄, MgO, Mn₃O₄, SiO₂, and ZnO. In a further aspect, most of the elements in the EAFD are in the oxide form.

In various aspects, the disclosed methods and compositions comprising EAFD provide numerous environmental advantages. In one aspect, the use of EAFD according to the present invention provides an effective means of EAFD disposal. In a further aspect, the disclosed methods and compositions, by utilizing EAFD, reduce potential environment problems associated with EAFD disposal. In a yet further aspect, the disclosed methods and compositions eliminate the need to dispose of EAFD in a landfill. In a still further aspect, the reduction in EAFD disposal frees landfill space.

In another aspect, the disclosed methods and compositions utilize untreated EAFD, thereby avoiding the cost associated with pretreatment of EAFD.

2. Method for Recovering Metal Oxide from EAFD

In one aspect, the invention comprises a method for preparing Electric Arc Furnace dust (EAFD) for metal recovery, comprising:

-   -   a) mixing the EAFD comprising zinc oxide or lead oxide, or a         mixture of both with a liquid and a binder to produce an EAFD         mixture;     -   b) producing a shaped EAFD pellet; and     -   c) drying the shaped EAFD pellet.

The method for preparing EAFD for metal recovery can use methods, techniques, or compositions from the other disclosed methods.

In one aspect, the shaped EAFD pellet can be produced in a rotating balling disc or a drum.

In a further aspect, the zinc oxide or lead oxide, or a mixture of both can be present in an amount from about 0.01 wt % to about 50 wt %, based on the total weight of the EAFD, including exemplary values of 0.40 wt %, 0.50 wt %, 2 wt %, 4 wt %, 6 wt %, 8 wt %, 10 wt %, 13 wt %, 15 wt %, 17 wt %, 20 wt %, 23 wt %, 25 wt %, 27 wt %, 30 wt %, 33 wt %, 35 wt %, 37 wt %, 40 wt %, 43 wt %, 45 wt %, 46 wt %, and 48 wt %. In a still further aspect, the zinc oxide or lead oxide, or a mixture of both can be present in a range derived from any two of the above listed exemplary wt %. For example, the zinc oxide or lead oxide, or a mixture of both can be present in an amount from about 0.40 wt % to about 17 wt %.

In a further aspect, the EAFD is BHD. In another aspect, the EAFD dust can come from a steel plant or other source. In one aspect, the EAFD can be dried in the sun to gain a sufficient strength so that these pellets can be transported.

In a further aspect, the liquid comprises water.

In a further aspect, the liquid can be present in an amount from about 6.0 wt % to about 12 wt %, based on the total weight of the EAFD mixture, which includes the binder and liquid, including exemplary values of 6.0 wt %, 8.0 wt %, 10 wt %, and 12 wt %. In a still further aspect, the liquid can be present in a range derived from any two of the above listed exemplary wt %. For example, the liquid can be present in an amount from about 8.0 wt % to about 10.0 wt %, 6 wt % to 12 wt %, or 6 wt % to 8 wt %.

In a further aspect, the binder comprises carbon, burnt lime, bentonite, or molasses, or a mixture thereof. In a still further aspect, the binder is bentonite. In a yet further aspect, the binder is molasses.

In a further aspect, the binder can be present in an amount from about 0.01 wt % to about 5.0 wt %, based on the total weight of the EAFD mixture, which includes the binder and liquid, including the exemplary values of 0.25 wt %, 0.50 wt %, 0.75 wt %, 1.0 wt %, 1.5 wt %, 2.0 wt %, 2.5 wt %, 3 wt %, 3.5 wt %, 4 wt %, and 4.5 wt %. In a still further aspect, the binder can be present in a range derived from any two of the above listed exemplary wt %. For example, the binder can be present in an amount from about 0.25 wt % to about 1.0 wt %.

In a further aspect, the binder comprises carbon in an amount from about 10 wt % to about 25 wt % based on the total weight of the binder, including the exemplary values of 12 wt %, 14 wt %, 16 wt %, 18 wt %, 20 wt %, 22 wt %, and 24 wt %. In a still further aspect, the binder comprises carbon in a range derived from any two of the above listed exemplary wt %. For example, the binder can comprise carbon in an amount from about 16 wt % to about 18 wt % based on the total weight of the binder.

In a further aspect, the binder comprises molasses in an amount from about 0.01 wt % to about 5.0 wt %, based on the total weight of the EAFD mixture, including the exemplary values of 0.5 wt %, 1 wt %, 1.5 wt %, 2 wt %, 2.5 wt %, 3 wt %, 3.5 wt %, 4 wt %, and 4.5 wt %. In a still further aspect, the binder comprises molasses in a range derived from any two of the above listed exemplary wt %. For example, the binder can comprise molasses in an amount from about 1 wt % to about 2 wt %. In one aspect, the binder is molasses.

In one aspect, the bentonite, which is a trade name of a binder comprising sodium potassium silicate, is used in the binder herein. The binder can comprise bentonite in an amount ranging from 0 wt % to 4.5 wt %, based on the total weight of the EAFD mixture, which includes the binder and liquid, including exemplary values 0.5 wt %, 1 wt %, 1.5 wt %, 2 wt %, 2.5 wt %, 3 wt %, 3.5 wt %, and 4 wt %. In a still further aspect, the binder comprises bentonite in a range derived from any two of the above listed exemplary wt %. For example, the binder can comprise bentonite in a range from 0.5 wt % to 4 wt % based on the total weight of the EAFD. In one aspect, the binder is bentonite.

In a further aspect, the EAFD can be mixed with the liquid and binder using conventional methods such as with an intensive mixer, such as a ROB Erich mixer or any other mixing equipment.

In one aspect, the method comprises producing an EAFD mixture. In another aspect, the EAFD mixture is a homogeneous composition.

In a further aspect, the EAFD pellet can be produced using any conventional method to produce a pellet, such as with a pan pelletizer or a drum pelletizer. In one aspect, forming a pellet can be desirable as a form to contain the dust in a leach-proof matrix for storing and disposing the EAFD.

In a further aspect, the EAFD pellet can be dried using any conventional method for drying, such as drying in the sun for a period of 1-4 days or heating in a drying oven.

In a further aspect, the average pellet size can range from about 7 mm to 18 mm, including exemplary values of 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, and 17 mm. In a still further aspect, the average pellet size can be in a range derived from any two of the above listed exemplary values. For example, the average pellet size can range from 8 mm to 17 mm.

In one aspect, the pellet is a spherical shape. In another aspect, the pellet can be any conventional pellet shape.

In one aspect, the pellet is produced using conventional methods. In another aspect, the pelletizing comprises the steps of grinding, sieving, mixing, agglomeration, binder optimization, and sintering. In a further aspect, the pelletizing uses a R02 Elrich mixer followed by pelletization on a disc pelletizer to produce the pellets.

The pellet has improved properties in physical, mechanical, chemical, and metallurgical properties. The pellet can be used in the method disclosed herein for recovering zinc or zinc oxide from EAFD. The pellet can be used as a way to transport the EAFD for metal recovery. The pellet can be used in the method disclosed herein for recovering lead, chlorine, sodium, or potassium, or a mixture thereof. The pellet can be used in the method disclosed herein for recovering iron oxide.

3. Method for Recovering Zinc/Zinc Oxide/Zinc Complex from EAFD

In one aspect, the invention comprises a method for recovering zinc from Electric Arc Furnace dust (EAFD), comprising:

-   -   a) heating the EAFD comprising at least one metal comprising         zinc in an inert gas atmosphere at a temperature ranging from         700° C. to 1100° C.; and     -   b) evaporating the at least one metal comprising zinc from the         EAFD and collecting the at least one metal.

The method for recovering zinc from EAFD can use methods, techniques, or compositions from the other disclosed methods.

FIG. 1 shows a flow diagram for the Caustic Soda Leaching Process for the extraction of zinc from EAFD of one aspect of the invention herein. FIG. 1 shows the inventive process for recovering the zinc using heating and evaporation.

In a further aspect, the zinc comprises zinc metal, zinc oxide or a complex of zinc and another metal oxide, or a mixture thereof. In a still further aspect, the zinc comprises zinc oxide. In yet a further aspect, the zinc comprises a complex of zinc and a metal oxide. In another aspect, the metal oxide of the complex comprises iron oxide. The complex of zinc and iron oxide can be zinc ferrite (ZnO.Fe₂O₃, franklinite). In one aspect, the zinc can comprise approximately 50 wt % in the zinc ferrite form based on the total weight of the zinc. The removal of the zinc from the EAFD can reduce the environmental liability and/or can create a value-added product by collecting the zinc.

In a further aspect, the zinc can be present in an amount from about 0.01 wt % to about 50 wt %, based on the total weight of the EAFD, including the exemplary values of including exemplary values of 0.40 wt %, 0.50 wt %, 2 wt %, 4 wt %, 6 wt %, 8 wt %, 10 wt %, 13 wt %, 15 wt %, 17 wt %, 20 wt %, 23 wt %, 25 wt %, 27 wt %, 30 wt %, 33 wt %, 35 wt %, 37 wt %, 40 wt %, 43 wt %, 45 wt %, 46 wt %, and 48 wt %. In a still further aspect, the zinc can be present in a range derived from any two of the above listed exemplary wt %. For example, the zinc can be present in an amount from about 2.0 wt % to about 46 wt %.

In a further aspect, the EAFD is BHD. In another aspect, the EAFD can come from a steel plant or other source. In a yet further aspect, the EAFD is in the form of a pellet.

In a further aspect, the average EAFD pellet size can range from about 7 mm to 18 mm, including exemplary values of 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, and 17 mm. In a still further aspect, the average pellet size can be in a range derived from any two of the above listed exemplary values. For example, the average pellet size can range from 8 mm to 17 mm.

In a further aspect, the inert gas comprises N₂, Ar, CO, or H₂, or a mixture thereof. In a still further aspect, the inert gas comprises Ar, CO, or H₂, or a mixture thereof. In yet a further aspect, the inert gas comprises CO or H₂, or a mixture thereof. In an even further aspect, the inert gas is N₂. In a still further aspect, the inert gas is Ar. In yet a further aspect, the inert gas is CO. In an even further aspect, the inert gas is H₂.

In a further aspect, the EAFD can be heated using a Static Reduction Reactor or any other suitable heating device.

In a further aspect, the Static Reduction Reactor further comprises

-   -   a) a system to supply and regulate the gases,     -   b) a reductible tube of heat resistant steel,     -   c) a weighing device to determine the oxygen loss at regular         intervals,     -   d) an electrically heated furnace to heat the test portion to         the specified temperature, and/or     -   e) a chart recorder to record the weight loss and a control         panel to control the flow and pressure of gas supplied.

In a further aspect, the EAFD can be heated at a temperature of from about 700° C. to about 1100° C., including the exemplary values of 750° C., 800° C., 900° C., 1000° C., and 1050° C. In a still further aspect, the EAFD can be heated in a range derived from any two of the above listed exemplary temperatures. For example, the EAFD pellets can be heated at a temperature from about 750° C. to about 1050° C.

In a further aspect, the at least one metal comprising zinc was evaporated until there is no more or substantially no more loss of weight from the EAFD source.

In one aspect, the zinc is evaporated and exits with at least one exhaust gas. The gases can be cooled and can be filtered in a cloth filter to collect a powder. The powder can comprise Zn and/or ZnO. The powder is filtered from the gas which can comprise Pb, Na, and/or K. The Pb, Na, and/or K can be in a compound with chlorine. In one aspect, the Na or K in the form of NaCl or KCl, respectively can be dissolved in water and removed.

In a further aspect, the invention further comprises re-oxidizing the zinc to form zinc oxide and collecting the zinc oxide.

4. Method for Recovering an Impurity

In a further aspect, the invention comprises a method for recovering an impurity from Electric Arc Furnace dust (EAFD), comprising:

-   -   a) heating the EAFD comprising an impurity in an inert gas         atmosphere at a temperature ranging from 700° C. to 1100° C.;         and     -   b) evaporating the impurity from the EAFD and collecting the         impurity.

The method for recovering an impurity from EAFD can use methods, techniques, or compositions from the other disclosed methods.

In a further aspect, the impurity comprises lead, chlorine, sodium, or potassium, or a mixture thereof. In a still further aspect, the impurity comprises lead, chlorine, or sodium, or a mixture thereof. In yet a further aspect, the impurity comprises lead or chlorine, or a mixture thereof. In an even further aspect, the impurity is lead. In a still further aspect, the impurity is chlorine. In yet a further aspect, the impurity is sodium. In an even further aspect, the impurity is potassium. The removal of the impurity from EAFD can reduce the environmental liability and/or can create a value-added product by collecting the metal.

In a further aspect, the impurity can be present in an amount from about 0.01 wt % to about 20 wt %, based on the total weight of the EAFD, including the exemplary values of 0.35 wt %, 0.40 wt %, 0.50 wt %, 1.8 wt %, 3.0 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, 15 wt %, 16 wt %, 17 wt %, 18 wt %, and 19 wt %. In a still further aspect, the impurity can be present in a range derived from any two of the above listed exemplary wt %. For example, the impurity can be present in an amount from about 0.5 wt % to about 1.8 wt %.

In a further aspect, the impurity further comprises chromium, cadmium, manganese, copper, silicon, calcium, magnesium, aluminum, carbon, or sulfur, or a mixture thereof. In a still further aspect, the impurity further comprises chromium, cadmium, manganese, copper, silicon, calcium, or magnesium, or a mixture thereof. In yet a further aspect, the impurity further comprises chromium, cadmium, manganese, silicon, carbon, or magnesium, or a mixture thereof. In an even further aspect, the impurity further comprises calcium or magnesium, or a mixture thereof. In an even further aspect, the impurity further comprises calcium.

In a further aspect, the EAFD is BHD. In another aspect, the EAFD is in the form of a pellet.

In a further aspect, the average EAFD pellet size can range from about 7 mm to 18 mm, including exemplary values of 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, and 17 mm. In a still further aspect, the average pellet size can be in a range derived from any two of the above listed exemplary values. For example, the average pellet size can range from 8 mm to 17 mm.

In a further aspect, the inert gas comprises N₂, Ar, CO, or H₂, or a mixture thereof. In a still further aspect, the inert gas comprises Ar, CO, or H₂, or a mixture thereof. In yet a further aspect, the inert gas comprises CO or H₂, or a mixture thereof. In an even further aspect, the inert gas is N₂. In a still further aspect, the inert gas is Ar. In yet a further aspect, the inert gas is CO. In an even further aspect, the inert gas is H₂.

In a further aspect, the EAFD can be heated using a Static Reduction Reactor.

In a further aspect, the Static Reduction Reactor further comprises

-   -   a) a system to supply and regulate the gases,     -   b) a reductible tube of heat resistant steel,     -   c) a weighing device to determine the oxygen loss at regular         intervals,     -   d) an electrically heated furnace to heat the test portion to         the specified temperature, and/or     -   e) a chart recorder to record the weight loss and control panel         to control the flow and pressure of gas supplied.

In a further aspect, the EAFD pellet can be heated at a temperature from about 700° C. to about 1100° C., including the exemplary values of 750° C., 800° C., 900° C., 1000° C., and 1050° C. In a still further aspect, the EAFD pellet can be heated in a range derived from any two of the above listed exemplary temperatures. For example, the EAFD pellet can be heated at a temperature from about 750° C. to about 1050° C.

In one aspect, the metal is evaporated under inert atmosphere.

In a further aspect, the at least one metal is evaporated until there is no more loss of weight.

In one aspect, the evaporated impurity is collected by cooling it to form a solid powder condensate and filtering and collecting in a bag filter.

5. Method for Recovering Iron Oxide from EAFD

In one aspect, the invention comprises a method for recovering iron oxide from Electric Arc Furnace dust (EAFD), comprising:

-   -   a) heating the EAFD comprising iron oxide and at least one metal         in an inert gas atmosphere at a temperature ranging from 700° C.         to 1100° C.;     -   b) separating the iron oxide by evaporating the at least one         metal from the EAFD and leaving the iron oxide as a residue.

The method for recovering iron oxide from EAFD can use methods, techniques, or compositions from the other disclosed methods.

In a further aspect, the iron can be present as iron oxide or as a complex of zinc and iron oxide, or a mixture thereof. In a still further aspect, the iron can be present as iron oxide. In yet a further aspect, the iron can be present as a complex of zinc and iron oxide. The removal of the metal from the EAFD can reduce the environmental liability and/or can create a value-added product by collecting the iron oxide.

In a further aspect, the metal further comprises zinc, lead, chromium, cadmium, manganese, copper, silicon, calcium, magnesium, aluminum, carbon, sulfur, sodium, potassium, or chlorine, or a mixture thereof. In a still further aspect, the metal further comprises zinc, lead, chromium, cadmium, manganese, copper, silicon, calcium, magnesium, sodium, potassium, or chlorine, or a mixture thereof. In yet a further aspect, the metal further comprises zinc, lead, chromium, cadmium, manganese, silicon, carbon, magnesium, sodium, potassium, or chlorine, or a mixture thereof. In an even further aspect, the metal further comprises zinc, lead, sodium, potassium, or chlorine, or a mixture thereof. In an even further aspect, the metal further comprises zinc, or lead, or a mixture thereof. In a still further aspect, the metal further comprises zinc. In yet a further aspect, the metal further comprises lead.

In a further aspect, the iron can be present in an amount from about 0.01 wt % to about 68 wt %, based on the total weight of the EAFD, including the exemplary values of including exemplary values of 0.40 wt %, 0.50 wt %, 2 wt %, 4 wt %, 6 wt %, 8 wt %, 10 wt %, 13 wt %, 15 wt %, 17 wt %, 20 wt %, 23 wt %, 25 wt %, 27 wt %, 30 wt %, 33 wt %, 35 wt %, 37 wt %, 40 wt %, 43 wt %, 45 wt %, 46 wt %, 48 wt %, 50 wt %, 52 wt %, 54 wt %, 56 wt %, 58 wt %, 60 wt %, 62 wt %, 64 wt %, and 66 wt %. In a still further aspect, the iron can be present in a range derived from any two of the above listed exemplary wt %. For example, the iron can be present in an amount from about 10 wt % to about 45 wt %.

In a further aspect, the other metals detailed above can be present in an amount from about 0.01 wt % to about 68 wt %, based on the total weight of the EAFD, including the exemplary values of including exemplary values of 0.2 wt %, 0.3 wt %, 0.40 wt %, 0.50 wt %, 2 wt %, 4 wt %, 6 wt %, 8 wt %, 10 wt %, 13 wt %, 15 wt %, 17 wt %, 20 wt %, 23 wt %, 25 wt %, 27 wt %, 30 wt %, 33 wt %, 35 wt %, 37 wt %, 40 wt %, 43 wt %, 45 wt %, 46 wt %, 48 wt %, 50 wt %, 52 wt %, 54 wt %, 56 wt %, 58 wt %, 60 wt %, 62 wt %, 64 wt %, and 66 wt %. In a still further aspect, the other metals detailed above can be present in a range derived from any two of the above listed exemplary wt %. For example, the other metals detailed above can be present in an amount from about 0.01 wt % to about 0.3 wt %.

In a further aspect, the EAFD is BHD. In another aspect, the EAFD is in the form of a pellet.

In a further aspect, the average pellet size can range from about 7 mm to 18 mm, including exemplary values of 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, and 17 mm. In a still further aspect, the average pellet size can be in a range derived from any two of the above listed exemplary values. For example, the average pellet size can range from 8 mm to 17 mm.

In a further aspect the inert gas comprises N₂ or Ar or a mixture thereof. In a further aspect, the inert gas is N₂. In a still further aspect, the inert gas is Ar.

In a further aspect, the EAFD can be heated using a Static Reduction Reactor.

In a further aspect, the Static Reduction Reactor further comprises

-   -   a) a system to supply and regulate the gases,     -   b) a reductible tube of heat resistant steel,     -   c) a weighing device to determine the oxygen loss at regular         intervals,     -   d) an electrically heated furnace to heat the test portion to         the specified temperature, and/or     -   e) a chart recorder to record the weight loss and control panel         to control the flow and pressure of gas supplied.

In a further aspect, the EAFD can be heated at a temperature from about 700° C. to about 1100° C., including the exemplary values of 750° C., 800° C., 900° C., 1000° C., and 1050° C. In a still further aspect, the EAFD can be heated in a range derived from any two of the above listed exemplary temperatures. For example, the EAFD can be heated at a temperature from about 750° C. to about 1050° C.

In one aspect, the at least one metal comprises zinc, zinc oxide, and/or zinc ferrite. In a further aspect, the zinc oxide and/or zinc ferrite can be dissociated. In another aspect, the zinc is evaporated.

In one aspect, the iron oxide is separated from the oxide of calcium, magnesium, silicon, and/or aluminum. In another aspect, the oxide of calcium, magnesium, silicon, and/or aluminum is left behind in the pellet.

In another aspect, the residual pellet comprises iron oxide and/or the oxide of calcium, silicon, aluminum, and/or magnesium. In a further aspect, the pellet can be collected from the sintering tube after cooling.

In one aspect, the iron oxide is present in a purity of 45 wt % to 80 wt % based on the total weight of the EAFD, including exemplary values of 50 wt %, 55 wt %, 60 wt %, 65 wt %, 70 wt %, and 75 wt %. In a still further aspect, the iron oxide is present in a purity derived from any two of the above listed exemplary wt %. For example, the iron oxide is present in a purity of 55 wt % to 70 wt %.

B. ASPECTS

The disclosed compositions and methods include at least the following aspects.

Aspect 1: A method for preparing Electric Arc Furnace dust (EAFD) for metal recovery, comprising:

-   -   a) mixing the EAFD comprising zinc oxide or lead oxide, or a         mixture of both, with a liquid and a binder to produce an EAFD         mixture;     -   b) producing a shaped EAFD pellet; and     -   c) drying the shaped EAFD pellet.

Aspect 2: The method according to aspect 1, wherein the EAFD is Bag House Dust (BHD).

Aspect 3: The method according to any one of aspects 1-2, wherein the metal oxide is zinc oxide.

Aspect 4: The method according to any one of aspects 1-3, wherein the metal oxide is lead oxide.

Aspect 5: The method according to any one of aspects 1-4, wherein the liquid is water.

Aspect 6: The method according to any one of aspects 1-5, wherein the liquid is present in an amount from about 6.0 wt % to 12.0 wt %, based on the total weight of the EAFD mixture.

Aspect 7: The method according to any one of aspects 1-6, wherein the liquid is present in amount from about 6.0 wt % to 10.0 wt %, based on the total weight of the EAFD mixture.

Aspect 8: The method according to any one of aspects 1-7, wherein the liquid is present in amount from about 6.0 wt % to 8.0 wt %, based on the total weight of the EAFD mixture.

Aspect 9: The method according to any one of aspects 1-8, wherein the binder is present in an amount from about 0.01 wt % to about 5.0 wt %, based on the total weight of the EAFD mixture.

Aspect 10: The method according to any one of aspects 1-9, wherein the binder is present in an amount of about 0.25 wt %, based on the total weight of the EAFD mixture.

Aspect 11: The method according to any one of aspects 1-10, wherein the binder is present in an amount of about 0.50 wt %, based on the total weight of the EAFD mixture.

Aspect 12: The method according to any one of aspects 1-11, wherein the binder is present in an amount of about 0.75 wt %, based on the total weight of the EAFD mixture.

Aspect 13: The method according to any one of aspect 1-12, wherein the binder is present in an amount of about 1.00 wt %, based on the total weight of the EAFD mixture.

Aspect 14: The method according to any one of aspects 1-13, wherein the binder is present in an amount of about 1.50 wt %, based on the total weight of the EAFD mixture.

Aspect 15: The method according to any one of aspects 1-14, wherein the binder is present in an amount of about 2.00 wt %, based on the total weight of the EAFD mixture.

Aspect 16: The method according to any one of aspects 1-15, wherein the average pellet size is from about 7.0 to 18 mm.

Aspect 17: A method for recovering zinc from Electric Arc Furnace dust (EAFD), comprising:

-   -   a) heating the EAFD comprising at least one metal comprising         zinc in an inert gas atmosphere at a temperature ranging from         700° C. to 1100° C.; and     -   b) evaporating the at least one metal comprising zinc from the         EAFD and collecting the at least one metal.

Aspect 18: The method according to aspect 17, wherein the at least one metal is zinc.

Aspect 19: The method according to any one of aspects 17-18, wherein the EAFD is Bag House Dust (BHD).

Aspect 20: The method according to any one of aspects 17-19, wherein the inert gas comprises N₂ or Ar, or a mixture thereof.

Aspect 21: The method according to any one of aspects 17-20, wherein the inert gas comprises Ar.

Aspect 22: The method according to any one of aspects 17-21, wherein the inert gas is N₂.

Aspect 23: The method according to any one of aspects 17-22, wherein the method comprises re-oxidizing the zinc to form zinc oxide and collecting the zinc oxide.

Aspect 24: The method according to any one of aspects 17-23, wherein the EAFD is a pellet.

Aspect 25: A method for recovering an impurity from Electric Arc Furnace dust (EAFD), comprising:

-   -   a) heating the EAFD comprising an impurity in an inert gas         atmosphere at a temperature ranging from 700° C. to 1100° C.;         and     -   b) evaporating the impurity from the EAFD and collecting the         impurity.

Aspect 26: The method according to aspect 25, wherein the EAFD is Bag House Dust (BHD).

Aspect 27: The method according to any one of aspects 25-26, wherein EAFD is in the form of a pellet.

Aspect 28: The method according to any one of aspects 25-27, wherein the impurity comprises lead, chlorine, or sodium, or a mixture thereof.

Aspect 29: The method according to any one of aspects 25-28, wherein the impurity comprises lead, or chlorine, or a mixture thereof.

Aspect 30: The method according to any one of aspects 25-29, wherein the impurity comprises lead.

Aspect 31: The method according to any one of aspects 25-30, wherein the impurity comprises chlorine.

Aspect 32: The method according to any one of aspects 25-31, wherein the impurity comprises sodium.

Aspect 33: The method according to any one of aspects 25-32, wherein the impurity comprises potassium.

Aspect 34: The method according to any one of aspects 25-33, wherein the inert gas comprises N₂ or Ar, or a mixture thereof.

Aspect 35: The method according to any one of aspects 25-34, wherein the inert gas is N₂.

Aspect 36: The method according to any one of aspects 25-35, wherein the inert gas is Ar.

Aspect 37: The method according to any one of aspects 28-36, wherein the method comprises re-oxidizing the lead to form lead oxide and collecting the lead oxide.

Aspect 38: The method according to any one of aspects 25-37, wherein the average pellet size is from about 7.0 to 18 mm.

Aspect 39: A method for recovering iron oxide from Electric Arc Furnace dust (EAFD), comprising:

-   -   a) heating the EAFD comprising iron oxide and at least one metal         in an inert gas atmosphere at a temperature ranging from 700° C.         to 1100° C.; and     -   b) separating the iron oxide by evaporating the at least one         metal from the EAFD and leaving the iron oxide as a residue.

Aspect 40: The method according to aspect 39, wherein the EAFD is Bag House Dust (BHD).

Aspect 41: The method according to any one of aspects 39-40, wherein the inert gas comprises N₂ or Ar, or a mixture thereof.

Aspect 42: The method according to any one of aspects 39-41, wherein the inert gas is N₂.

Aspect 43: The method according to any one of aspects 39-42, wherein the inert gas is Ar.

Aspect 44: The method according to any one of aspects 39-43, EAFD is in the form of a pellet.

Aspect 45: The method according to any one of aspects 39-44, wherein the at least one metal comprises zinc, lead, chromium, cadmium, manganese, copper, silicon, calcium, magnesium, aluminum, carbon, sulfur, sodium, potassium, or chlorine, or a mixture thereof.

C. EXPERIMENTAL

The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices and/or methods claimed herein are made and evaluated, and are intended to be purely exemplary of the invention and are not intended to limit the scope of what the inventors regard as their invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in ° C. or is at ambient temperature, and pressure is at or near atmospheric.

Several methods for preparing the compounds of this invention are illustrated in the following Examples. Starting materials and the requisite intermediates are in some cases commercially available, or can be prepared according to literature procedures or as illustrated herein.

The following exemplary compounds of the invention were synthesized. The Examples are provided herein to illustrate the invention, and should not be construed as limiting the invention in any way. The Examples are typically depicted in free base form, according to the IUPAC naming convention. However, some of the Examples were obtained or isolated in salt form.

1. Example 1 a. Preparation and Evaluation of Pellets

Pelletizing included the steps of grinding and sieving, mixing, agglomeration, green strength testing, and binder optimization; evaluation included sintering, and testing of the pellets compressive strength after heating. BHD contained more than 95% of particle size less than 90 microns, which did not require any further grinding, was used. Only sieving was conducted to remove the dust fraction >90 microns. Bentonite and burnt lime were used as binders. The optimum binder addition was determined for each of the mixtures. All the samples were pelletized and evaluated to determine the physical and metallurgical properties of the pellets produced.

Binder additions of 0.25, 0.50, 0.75, 1.00, 1.5 and 2 wt % binder, based on the total EAFD weight, respectively were added to determine the optimum binder content. Batches (3-5 kg) of each sample were premixed with the different binder additives in an RO2 Elrich mixer followed by pelletization on a disc pelletizer to produce pellets with size range of 09 to 16 mm. Water, 8-10% by wt. based on the total weight of the EAFD, was added before mixing. All the pellets samples were dried in the sun in open air for a couple of days. The drop number and compression tests were conducted on 12 different pellets for each type of sample produced to determine the binder additive with optimum pellet strength. The average, minimum, maximum strengths and standard deviation were calculated for all the samples.

B. Pellets Properties

Table 1 below shows the Drop Number of BHD pellets. All the green pellets were optimized to demonstrate a Drop Number of more than 4. A minimum of 3 drops are required for pellets to be transported for sintering in a commercial pelletizing/sintering plant.

TABLE 1 Typical drop number of BHD green EAFD pellets with varying contents of moisture and binder after optimizing drop number Mois- Average ture Binder, Drop Sample weight weight Test Test Test Test Test Number No % % 1 2 3 4 5 Score 1 8 2.00 6 6 5 4 5 5.2 2 9 2.00 9 9 10 10 12 10 3 10 2.00 7 8 8 7 9 7.8 4 8 1.50 6 8 5 7 6 6.4 5 9 1.50 6 7 7 5 6 6.2 6 10 1.50 3 4 4 5 6 4.2 7 11 1.25 3 4 4 3 5 3.8 8 10 1.25 3 3 4 5 6 4.2 9 9 1.25 5 7 4 4 4 4.8 10 8 1.25 6 7 6 6 5 6

The pellets were dried in the sun only. No heating was used for strength enhancement. Table 2 below shows the compressive strength of dried BHD pellets. All the dried pellets were optimized to demonstrate Compressive Strength in the range of 40-108 kg per pellet. This was measured using Instron Compression strength testing machine.

TABLE 2 Typical Compressive of Strength of Dried Pellets after Optimizing the Binder Proportion Pellet Number Compressive Strength, kgf/Pellet 1 82 2 42 3 89 4 78 5 56 6 41 7 48 8 108 9 52

2. Example 2 Heating and Separation of Zinc by Evaporization

The heating/sintering of BHD pellets and evaporization of volatiles was conducted in a Static Reduction Reactor.

The specific conditions involved in the sintering test were: heating to the desired temperature in the desired gas atmosphere; sintering in a fixed bed; and sintering by means of inert gases and a sample having a size range of 12 mm-16 mm. The current study was conducted according to the BS6598-1985 corresponding to ISO 4695-1984 (used for evaluating iron ore reducibility) with some deviations modification to correlate the test requirements. Non-isothermal sintering was used. Instead of a mixture of carbon monoxide and nitrogen, an inert gas was used.

The apparatus consisted of a reduction furnace supplied by Labomatic fitted with the following provisions:

I. A system to supply and regulate the gases II. A reduction tube of heat resistant steel III. A weighing device to determine the oxygen loss at regular intervals IV. An electrically heated furnace to heat the test portion to the specified temperature V. A chart recorder and control panel

The sintering tube was made of non-scaling, heat resistance metal to withstand temperatures of higher than 1100° C. The wire grid was mounted in the reduction tube at the quarter depth from the bottom of the retort, for supporting the raw material test portion. The weight of the sample used for each sintering test was 500 g±2 g. The weighing device with this equipment was capable of weighing the load to an accuracy of 1 g. The weighing device was checked for sensitivity at regular intervals.

Each sample containing 500 g of dried BHD pellets was then heated at 700-1100° C. in an atmosphere of N₂, to study the effects of this inert gas on zinc removal. The samples were heated until there is no more loss of weight. The samples were left in the furnace to cool down to room temperature. The residual pellets and vapor condensates were analyzed for chemical composition using XRF, C & S Analyzers and phases using XRD techniques.

3. Example 3 Sintering of BHD Pellets in N₂ Atmosphere

The samples were sintered in a furnace under a N₂ atmosphere at different temperatures. The weight of the sample before sintering was 500±2 g. The weight of the sample was taken after the sintering as well. FIG. 2 shows the weight loss of BHD pellets in N₂ atmosphere at different temperatures.

FIG. 3 shows the comparison of Zn content of BHD pellets sintered in N₂ atmosphere at various temperatures.

FIG. 4 is a graph depicting the Zn and Pb content of pellets sintered under a nitrogen atmosphere at various temperatures.

FIG. 5 gives the Zn and Pb content of vapor condensate extracted from BHD pellets by sintering in nitrogen at various temperatures.

FIG. 6 gives the weight % of Zn removed from BHD pellets during sintering in a N₂ atmosphere at different temperatures. The values were summarized in Table 3 below. As shown, 85% and 97% of the Zn could be removed from BHD at temperatures 1000° C. and 1100° C. in a N₂ atmosphere, respectively. However, oxygen in iron oxide could not be removed with N₂. Hence, the residue comprises iron in the form of iron oxide. The chemical analysis of the vapor condensate showed that the total zinc content was in the form of metallic Zn and ZnO, and it was mixed with PbO, Na, K, and Cl. Further hydrometallurgical treatment was required to separate all these constituents.

TABLE 3 Zn content and percentage of Zn removed from BHD pellets Entry Zn Content in BHD % Zn No. T (° C.) Pellet (wt %) Removed 1 Room 15.39 (Before sintering) 0 temperature 2 900 14.12 (After sintering)  8.3 3 950 3.85 (After sintering) 75 4 1000 2.20 (After sintering) 85.7 5 1050 1.28 (After sintering) 91.7 6 1100 0.37 (After sintering) 97.6

The comparison of the weight loss of other elements is shown in FIG. 7. The elements Pb, K, Na and Cl were removed at temperatures starting at about 900° C. The analysis of the vapor condensate indicated that Zn occurred in the form of elemental Zn and ZnO and it was mixed with PbO, Na, K and Cl. Table 4 summarizes the composition of the elements found in the condensate upon sintering at 1000° C. Further hydrometallurgical treatment was required to separate all these constituents.

TABLE 4 Chemical Composition of Pellets and Vapor Condensate produced in N₂ atmosphere at 1000° C. Compound Pellet Concentration (wt %) Condensate Concentration MgO 1.42 Trace Al₂O₂ 0.648 Trace SiO₂ 4.72 0.0056 P₂O₅ 0.324 0.22 S 0.187 0.101 CI 0.0757 6.7 K₂O 0.715 13.87 CaO 18.13 0.18 TiO₂ 0.0923 0.014 MnO 1.272 0.01 Ni 0.0475 0.0296 Cu 0.0476 0.248 ZnO 5.125 66.7568 Cd Trace 0.046 Sn 0.0082 0.022 PbO 0.146 11.53 Fe₂O₃ 66.8949 0.25

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims. 

1. A method for preparing Electric Arc Furnace dust (EAFD) for metal recovery, comprising: a) mixing the EAFD comprising zinc oxide or lead oxide, or a mixture of both, with a liquid and a binder to produce an EAFD mixture; b) producing a shaped EAFD pellet; and c) drying the shaped EAFD pellet.
 2. (canceled)
 3. The method according to claim 1, wherein the metal oxide is zinc oxide.
 4. The method according to claim 1, wherein the metal oxide is lead oxide.
 5. The method according to claim 1, wherein the liquid is water.
 6. The method according to claim 1, wherein the liquid is present in an amount from about 6.0 wt % to 12.0 wt %, based on the total weight of the EAFD mixture.
 7. (canceled)
 8. (canceled)
 9. The method according to claim 1, wherein the binder is present in an amount from about 0.01 wt % to about 5.0 wt %, based on the total weight of the EAFD mixture. 10-15. (canceled)
 16. The method according to claim 1, wherein the average pellet size is from about 7.0 to 18 mm.
 17. A method for recovering zinc from Electric Arc Furnace dust (EAFD), comprising: a) heating the EAFD comprising at least one metal comprising zinc in an inert gas atmosphere at a temperature ranging from 700° C. to 1100° C.; and b) evaporating the at least one metal comprising zinc from the EAFD and collecting the at least one metal.
 18. The method according to claim 17, wherein the at least one metal is zinc. 19-22. (canceled)
 23. The method according to claim 17, wherein the method comprises reoxidizing the zinc to form zinc oxide and collecting the zinc oxide.
 24. (canceled)
 25. A method for recovering an impurity from Electric Arc Furnace dust (EAFD), comprising: a) heating the EAFD comprising an impurity in an inert gas atmosphere at a temperature ranging from 700° C. to 1100° C.; and b) evaporating the impurity from the EAFD and collecting the impurity.
 26. (canceled)
 27. The method according to claim 25, wherein EAFD is in the form of a pellet.
 28. The method according to claim 25, wherein the impurity comprises lead, chlorine, or sodium, or a mixture thereof. 29-36. (canceled)
 37. The method according to claim 25, wherein the method comprises reoxidizing the lead to form lead oxide and collecting the lead oxide.
 38. The method according to claim 25, wherein the average pellet size is from about 7.0 to 18 mm. 39-45. (canceled) 